1. Field of the Invention
The present invention relates to the scoring of glass and frangible workpieces, and particularly, to improvements in breaking the workpieces along the score lines and transporting resulting products.
2. Background Information
Frangible workpieces, such as glass products, are often scored to obtain the desired shape of the final product. Scoring entails cutting a groove, called a score line, partially through the thickness of the workpiece with the score lines defining the general shape of the final product. The scoring is generally performed with a sharp metal cutting wheel. Following the placement of scoring lines, the product is separated from the remaining sections of the workpiece along the score lines in a process commonly called breaking. The breaking of the scored workpiece entails generating a fracture through the thickness of the frangible workpiece within the score line which propagates along the score line. For the sake of clarification, xe2x80x9cbreakingxe2x80x9d within the context of this application refers to this fracturing along the score lines as opposed to the destruction of the workpiece. The breaking represents a critical step in defining the resulting edge of the product. Without a clean breaking procedure the product edge will not be sharp and well defined and may require a significant amount of subsequent processing, such as grinding. A poor break may also result in an unusable workpiece (here the workpiece may be considered xe2x80x9cbrokenxe2x80x9d in the generic sense of the word) resulting in yield loss in the overall process.
The scoring may be performed manually using hand-held scoring implements. For products made from large sheets, the process is commonly automated by scoring, also referred to as cutting, the large sheet or workpiece on an automated cutting table having a movable scoring or cutting head. In such automated cutting tables the movable cutting head is often controlled by a CNC controller to score the workpiece according to the desired pattern.
In current automated systems, the breaking of the scored workpiece along the score lines is problematic. Often the process if performed manually, prior to moving the product to subsequent processing. The manual breaking of the scored workpiece is labor intensive and time-consuming. Additionally, none of the existing processes, such as thermal breaking, pressure wheels, templates or the like, for breaking the scored workpiece provide a consistently clean break or product edge.
An object of the present invention is to overcome the aforementioned difficulty with the prior art and to provide a process and apparatus for efficiently and accurately breaking scored workpieces, such as glass sheets, and transporting the resulting products. A further object of the present invention is to provide a process and apparatus for breaking scored workpieces which provides a consistent clean break or edge to the product. A further object of the present invention is to provide an automatic breaking process and apparatus which is both easy and economical to manufacture and to use and is easy to install in existing processing lines.
The above objects are achieved by a process for breaking scored sheets according to the present invention. The process includes at least the steps of floating a scored sheet on a fluid medium and impacting the scored sheet from above the floated scored sheet. A process for cutting glass sheets according to the present invention includes the steps of: scoring each glass sheet on an automatic scoring table having a movable scoring head; transporting each scored glass sheet to a breaking table; floating each scored sheet on a fluid medium on the breaking table; and impacting each scored sheet from above the floated scored sheet to fracture the scored sheet along the score lines. One modification of the present invention may provide that the scoring and breakout are performed at the same station.
One embodiment of the present invention includes scoring the workpiece on a scoring table and including vent lines within selected sections of the workpiece. The impact of the scored workpiece moves the impacted locations of the workpiece at least halfway into the floated air cushion in less than 0.25 seconds. Additionally, the impact may be performed by vacuum cups engaging the final product at a single or plurality of locations. Air cylinders may be used for controlling the vertical movement of the vacuum cups. After breaking, the vacuum cups may be used to transport the product in a conventional fashion. A single or plurality of flat pads may be used in place of the vacuum cups. The vacuum cups are useful for subsequent transporting of the workpiece.
An apparatus according to the present invention includes at least a workpiece receiving, or breaking, table with a mechanism for floating a workpiece thereon on a fluid medium, and a workpiece impacting mechanism. The apparatus for cutting glass sheets according to the present invention includes: a mechanism for scoring each glass sheet, such as an automatic scoring table having a movable scoring head; a breaking table adjacent the automatic cutting table; a mechanism for transporting each scored glass sheet to the breaking table; a mechanism for floating each scored sheet on a fluid medium on the breaking table; and a mechanism for impacting each scored sheet from above the floated scored sheet to fracture the scored sheet along the score lines. A separate loading table and a separate table with a separate cutter for cutting score lines and/or vent lines may also be incorporated into the system for faster processing.
In one embodiment of the present invention the receiving table provides an air cushion for floating the glass at least {fraction (3/16)} of an inch. The impacting mechanism may move the impacted locations of the workpiece at least halfway into the floated air cushion in less than 0.25 seconds, with the impact mechanism formed by vacuum cups which engage the product at a plurality of locations, and with air cylinders used for controlling the vertical movement of the vacuum cups. After breaking, the vacuum cups may be used to transport the product in a conventional fashion.
These and other advantages of the present invention will be clarified in the description of the preferred embodiments taken together with the attached drawings wherein like reference numerals represent like elements throughout.